CN112285817A

CN112285817A - Near infrared optical interference filter with improved transmission

Info

Publication number: CN112285817A
Application number: CN202011335561.9A
Authority: CN
Inventors: 罗伯特·斯普瑞格; 白胜元
Original assignee: Metlong
Current assignee: Metlong; Materion Corp
Priority date: 2015-02-18
Filing date: 2016-02-18
Publication date: 2021-01-29
Also published as: WO2016134122A1; EP3259626B1; US12422605B2; KR20230140612A; JP2018506076A; EP4163683B1; US20160238759A1; KR20240134050A; TWI743031B; US20190212484A1; KR20170117533A; US20250389880A1; CN107209306B; US20220299688A1; EP3839585B1; EP4414756A3; CN107209306A; EP3259626A1; TW201643478A; EP4414756A2

Abstract

The interference filter comprises a layer stack comprising a plurality of layers at least: an amorphous hydrogenated silicon layer (a-Si:H,N) with added nitrogen and one or more layers of a dielectric material, For example _SiO2 , _SiOx , _SiOxNy , the dielectric material has a higher refractive index in the range of 1.9 to 2.7 _inclusive , and so on. Interference filters are designed to have passband center wavelengths in the range of 750-1000 nm inclusive. The addition of nitrogen in the a-Si:H,N layer provides improved transmission in the passband, while no large reduction in refractive index is observed in a-Si:H with comparable transmission. A layer of dielectric material having a higher index of refraction in the range of 1.9 to 2.7 inclusive provides a smaller angular shift than a similar interference filter using _SiO2 as the low index layer.

Description

Near infrared optical interference filter with improved transmission

The present application is a divisional application of the chinese patent application having application number 201680008448.5. The chinese patent application No. 201680008448.5 is a chinese national phase application of international application PCT/US2016/018429, which claims the benefit of US provisional application 62/117,598 entitled "NEAR INFRARED OPTICAL INTERFERENCE FILTERS WITH IMPROVED near infrared OPTICAL interference filter with IMPROVED transmittance" filed on 18.2.2015. U.S. provisional application 62/117,598 filed on 18.2.2015 is incorporated by reference herein in its entirety.

Technical Field

The following relates to the optical arts, optical filter arts, and related arts.

Background

Known transmission type interference filters use alternating silicon and silicon dioxide (SiO)₂) A stack of layers. Such devices are known for short and medium wave infrared down to about 1100nm, due to silicon and SiO₂Transparent in this range. The lower wavelength threshold (corresponding to the upper photon energy threshold) is controlled by the onset of absorption by silicon, which in its crystalline form has a bandgap of about 1.12 eV. A key advantage of silicon in these devices is its high refractive index. The spectral profile of the optical interference filter depends, among other things, on the illumination angle. As the angle increases, the filter switches to a shorter wavelength. This angular offset depends on the materials used and the distribution of these materials. A higher refractive index results in less angular shift. For narrow band filters, the angular offset limits the useful bandwidth of the filter when used in an optical system. In systems with large angular acceptance angles, filters configured to produce, for example, low angular offsets can have narrower passbands and therefore greater noise rejection than filters constructed from lower index materials.

To extend device operation toNear infrared, it is also known to hydrogenate silicon in order to use hydrogenated amorphous silicon (a-Si: H) and SiO₂Alternating layers of (a). By hydrosilation, material loss and refractive index are reduced. By this means, very high performance interference filters operating in the range of 800-.

Some improvements are disclosed herein.

Disclosure of Invention

In one exemplary aspect disclosed herein, an interference filter is disclosed that includes a layer stack including a plurality of layers, the plurality of layers having at least: a layer of amorphous hydrogenated silicon (a-Si: H, N) with added nitrogen and one or more layers of dielectric material having a refractive index lower than that of a-Si: H, N. As a non-limiting example, the one or more dielectric materials may include SiO₂Silicon Suboxide (SiO)_x) And/or silicon oxynitride (SiO)_xN_y). In some embodiments, the one or more dielectric materials comprise a layer of dielectric material having a refractive index in the range of 1.9 to 2.7 inclusive. In some embodiments, the a-Si: H, N has an atomic concentration of between 1% and 4% hydrogen and between 2% and 6% nitrogen. The layer stack may be supported by a transparent substrate, such as a glass substrate.

In another exemplary aspect disclosed herein, an interference filter comprises a stack of layers comprising alternating a-Si: H, N and silicon-based dielectric layers, wherein the interference filter has at least one pass band with at least one center wavelength in the range of 750-. As a non-limiting example, the silicon-based dielectric layer may comprise silicon oxide (SiO)_x) Layer and/or silicon oxynitride (SiO)_xN_y) And (3) a layer. In some embodiments, the a-Si: H, N has an atomic concentration of between 4% and 8% hydrogen and between 2% and 2% nitrogen. The layer stack may be supported by a transparent substrate, such as a glass substrate.

In another exemplary aspect disclosed herein, a method of fabricating a semiconductor device including alternating a-Si: H, N layers and SiO is disclosed_xMethod of interference filter of layers. The method includes sputtering silicon from a silicon target onto a filter substrate, and during sputtering,alternating between (i) the process gas including hydrogen and nitrogen to deposit a Si: H, N and (ii) the process gas including oxygen to deposit SiOx. Sputtering may include applying a negative bias to a silicon target and both a process gas including hydrogen and nitrogen and a process gas including oxygen include inert gas components. The inert gas may be, for example, argon. An interference filter manufactured by the process is also disclosed.

In another exemplary aspect disclosed herein, an interference filter includes a layer stack including a plurality of layers of which at least an amorphous hydrogenated silicon layer, and one or more layers of dielectric material having a refractive index lower than that of the amorphous hydrogenated silicon, including layers of dielectric material having a refractive index in the range of 1.9 to 2.7, inclusive. In some embodiments, the layer of dielectric material having a refractive index in the range of 1.9 to 2.7 inclusive comprises one or more layers including Si₃N₄，SiO_xN_y(where y is large enough to provide a refractive index of 1.9 or higher), Ta₂O₅，Nb₂O₅Or TiO₂. In some embodiments, the layer stack comprises at least one SiO next to a layer of dielectric material₂A layer having a refractive index in the range of 1.9 to 2.7 inclusive, without an intermediate layer of amorphous hydrogenated silicon. In some embodiments, the amorphous hydrogenated silicon includes nitrogen. In some such embodiments, the amorphous hydrogenated silicon comprising nitrogen has an atomic concentration of between 1% and 4% hydrogen and between 2% and 6% nitrogen.

Drawings

FIG. 1 schematically illustrates a sputter deposition system for fabricating a near-infrared optical interference filter having improved transmission and/or reduced angular offset as disclosed herein.

FIG. 2 schematically shows the effect of hydrogenation on the optical properties (transmittance and refractive index) of amorphous hydrogenated silicon (a-Si: H).

Fig. 3 schematically shows the effect of nitrogen additives on the optical properties (transmittance and refractive index) of a-Si: H at a fixed hydrogenation level.

FIG. 4 schematically illustrates an interference filter suitable for fabrication using the sputter deposition system of FIG. 1.

Detailed Description

As previously described, interference filters comprising a stack of layer cells with a layer of hydrogenated silicon (a-Si: H) are used to operate in the near infrared (800-. Referring briefly to fig. 2, it is recognized herein that this approach for near infrared has significant drawbacks. Increasing the hydrogenation of a-Si: H (that is, increasing the hydrogen content of a-Si: H) does reduce the loss for a fixed wavelength in the infrared (e.g., in the range of 800-.

The performance of narrow-band interference filters for high numerical aperture optical systems is a compromise between achieving high transmission and low angular shift in the near infrared region where material properties change rapidly. High transmission corresponds to a low extinction coefficient (obtainable with large amounts of hydrogen), while a small angular shift is achieved by a high refractive index (obtainable with small amounts of hydrogen).

Referring briefly to FIG. 3, the disclosed improvement involves the addition of a controlled amount of nitrogen to the a-Si: H layer of a silicon-based interference filter for the near infrared (800-. In other words, the improvement requires the replacement of a-Si: H with a-Si: H, N. As schematically shown in fig. 3, for a fixed wavelength in the infrared (e.g. in the 800-. The effect of adding nitrogen on the refractive index is much less than that of hydrogenation, especially for nitrogen percentages in the range of 10% nitrogen or less. Thus, this modification enables the fabrication of near infrared interference filters operating in the range of 800-.

On the other hand, replacing a-Si: H with a-Si: H, N for a given pass band width may provide improved transmission in the pass band. In this approach, replacing a-Si: H with a-Si: H, N enables the fabrication of near-infrared interference filters with improved transmission in the passband compared to equivalent a-Si: H based devices with the same refractive index step (and therefore the same spectral passband width). In fact, the inventors have found that the practical operating range of such a filter can be extended down to 750nm in such a design paradigm.

Those skilled in the art will recognize that the spectral range covered by the disclosed a-Si: H, N based interference filter includes a technologically important passband, such as the 850nm optical data communications window.

In some interference filter applications operating in this range, another consideration is the angular shift of the pass band. Conceptually, the angular shift is caused by the increase in ray path length through the layer as the angular deviation from normal incidence increases. This increase in path length corresponds to a change in phase delay that affects constructive/destructive interference to introduce an angular offset. If the normal incidence path length through the layer is d_LThen at an angle theta in the material_L(measured deviation from Normal, i.e. for Normal incidence θ_L0) the path length of the passing layer is d'_L＝d_L/cos(θ_L). Since the principle of Snell is_LIn relation to the angle of incidence θ of the light incident on the interference filter, assuming that the environment is air (n is 1), this makes θ_L＝arcsin(θ/n_L) Wherein n is_LIs the refractive index of the layer. Use identification

It can be written as

Thus, it can be seen that due to the small refractive index n of the layer_LThe effect of angular offset is worsened.

In conventional interference filter designs, it is generally desirable to maximize the refractive index contrast between the high and low index layers. In a silicon-based interference filter, the high refractive index layer is a-Si: H (which may be replaced by a-Si: H, N as disclosed herein), and silicon dioxide (SiO with N1.4-1.5)₂) As a low refractive index layer. However, this is not soBy replacing SiO with a higher refractive index material in some or all of the low refractive index layers of the interference filter₂To obtain a reduced angular offset of the interference filter operating in the range 750-1000 nm. In some contemplated embodiments, the replacement layer is a dielectric layer having a refractive index in the range of 1.9 to 2.7 inclusive. Some suitable Si compatible materials that provide these values include silicon nitride (Si with n-2.0-2.2)₃N₄) Silicon oxynitride (SiO)_xN_yY is large enough to provide a refractive index of 1.9 or higher), tantalum pentoxide (Ta with n-2.1-2.2)₂O₅) Niobium pentoxide (Nb with n-2.3-2.4)₂O₅) Or titanium dioxide (TiO with n-2.6)₂). In the exemplary embodiment shown herein, silicon nitride (Si) is used₃N₄). The high index a-Si: H or a-Si: H, N layer should have a hydrogen (and optionally nitrogen) content sufficient to provide the desired index contrast when compared to the low index layer.

In addition, to obtain the desired low angular offset for the design specification angle, only a higher refractive index dielectric material (e.g., Si) is used₃N₄) Replacing some SiO of the stack₂A layer may be sufficient. Optical design software (e.g., ray tracing simulators) can be used to optimize layer placement and thickness of materials with known indices of refraction in order to achieve the desired center-band, bandwidth, and angular-shift design fundamental characteristics.

Referring now to FIG. 1, a suitable manufacturing system is depicted. An exemplary system employs sputter deposition, however, other deposition methods are also contemplated, such as vacuum evaporation, electron beam evaporation, and the like. In general, a.c. (alternating current) sputtering or d.c. (direct current) sputtering may be used. The exemplary sputter deposition system includes a process chamber 10 containing a sputter target holder 12 and a substrate turntable 14. For exemplary deposition, a silicon target 16 (e.g., silicon wafer 16) is mounted in a sputter target holder 12. One or more substrates 20 are loaded into the substrate carousel 14. The substrate 20 is suitably made of a material such as glass, silicon dioxide or aluminum oxide, which is transparent in the wavelength range of interest (e.g., 800-1000nm or 750-1000 nm).

In sputter deposition, energetic particles are directed toward the target 16 (in this case, the silicon target 16), the particles having sufficient energy to remove (i.e., "sputter") material from the target, and then transfer (ballistically and/or under the influence of a magnetic or electric field) to the surface of the substrate 20 to coat the substrate 20 with the sputtered material. The exemplary sputter deposition system uses argon (Ar) gas from an exemplary argon (Ar) gas cylinder 22 or from another argon source as the energetic particles. An ionizing electric field is generated by applying a negative bias voltage (-V) to the target 16 to ionize the argon atoms, which then bombard the negatively biased target 16 under the influence of the electric field generated by the-V voltage bias to produce sputtering. On the other hand, substrate 20 is more forward biased than target 16, e.g., substrate 20 is grounded in the exemplary sputtering system of FIG. 1. In this exemplary configuration, the target 16 is the cathode of the circuit and the chamber 10 (and/or the substrate 20, e.g., the substrate turntable 14 may be grounded in some embodiments) is the anode of the circuit. Although argon is the sputtering gas in the exemplary embodiment, other inert gases that can be ionized, such as xenon, may alternatively be used.

Oxygen (O) is supplied for the deposition of silicon dioxide₂) A bottle 24 or other oxygen source. For depositing amorphous hydrogenated silicon with nitrogen additive (a-Si: H, N), hydrogen (H) is supplied₂) Bottle 26 or other source of hydrogen (e.g. ammonia, NH)₄Or silane, SiH₄) And nitrogen (N)₂) Bottle 30 or other nitrogen source. A gas inlet manifold 32 (shown schematically) is provided to allow a desired gas mixture into the process chamber 10 during the sputter deposition process. The flow regulator 34 is adjustable to set Ar, O, respectively₂，H₂And N₂The flow rate of (c). The process chamber 10 is also connected to a suitable exhaust 36 (e.g., with a scrubber or the like) to exhaust gases from the chamber 10. It is contemplated that other gas sources may be substituted for the exemplary O₂，H₂And N₂And (7) a bottle. Other suitable sources of nitrogen include ammonia (NH)₄) Or hydrazine (N)₂H₄). When using a source of ammonia or hydrazine including nitrogen and hydrogen, a calibration should be performed to account for the relative incorporation of nitrogen and hydrogen in the a-Si: H, N layer. Such as substrate temperature, target biasProcess parameters such as pressure (-V), chamber pressure, total flow rate, etc. may affect the relative incorporation of nitrogen and hydrogen. Providing two valves VA, VB for depositing SiO₂And a-Si, H and N. Valve VA controls the ingress of oxygen from oxygen source 24 into gas inlet manifold 32, while valve VB controls the ingress of the hydrogen/nitrogen mixture from hydrogen source 26 and nitrogen source 30. To be on SiO₂The deposition is rapidly switched with a-Si: H, N deposition, and the valves VA, VB are automatic valves whose actuators are controlled by an electronic sputter controller 40 according to a filter recipe 42. For example, the sputter controller 40 can include a digital-to-analog (D/a) converter, a high voltage source, and a microprocessor or microcontroller programmed to operate the D/a converter to generate electrical actuation signals to open or close the respective valves VA, VB in accordance with the filter recipe 42 and to operate the voltage source to apply the voltage-V to the target/cathode 16. The bottom right inset table 50 shown in FIG. 1 summarizes the deposition of SiO₂And a-Si, H, N for the setting of valves VA, VB, respectively. To deposit SiO₂Valve VA is opened to allow oxygen to enter gas inlet manifold 32 while valve VB is closed to shut off the hydrogen and nitrogen sources. The resulting process gas is an argon/oxygen mixture. To deposit a-Si: H, N, valve VA is closed to block oxygen and valve VB is opened to allow process gas comprising an argon/hydrogen/nitrogen mixture to enter gas inlet manifold 32. Note that argon source 22 is connected to gas inlet manifold 32 independently of valves VA, VB. Typically, a separate manually operable shut-off valve (not shown) is provided for each

gas source

22, 24, 26, 30 to enable each gas source to be manually shut off independently of the automatic valves VA, VB.

If it is further desired to replace some of the low index layers with a higher index material, an additional gas source may be provided in conjunction with a suitable valve arrangement. In the exemplary system of FIG. 1, to deposit silicon nitride (Si)₃N₄) Layer, providing additional nitrogen (N) controlled by valve VC₂) Bottle 25 or other nitrogen source. As further shown in Table 50, Si is achieved when valve VC is open and both valves VA and VB are closed₃N₄And (4) depositing. And deposition of SiO₂As such, the silicon component of the silicon nitride is supplied by the silicon-based sputtering target 20. The required stoichiometry is determined by using a suitably calibrated flow regulator on the operating nitrogen cylinder 25And (4) setting. Although not shown in FIG. 1, it should be understood that a similar arrangement may be used to deposit SiO with a refractive index of 1.9 or higher by opening both valves VA, VC with valve VB closed_xN_y. In order to replace non-silicon containing dielectric layers (e.g. Ta)₂O₅，Nb₂O₅Or TiO₂) The target holder 12 may have a plurality of target slots loaded with a silicon target and yet another slot loaded with a suitable target, for example comprising tantalum, niobium or titanium, for depositing a silicon-free dielectric layer. Alternatively, tantalum, niobium, titanium, and others may be provided from a gas source or other sources.

A manufacturing process for an exemplary interference filter suitable for execution using the manufacturing system of fig. 1 is described next. Initially, all

gas sources

22, 24, 26, 30 are manually turned off, the process chamber 10 is brought to atmospheric pressure and turned on, the targets 16 are loaded onto the target holders 12, and the substrates 20 are loaded onto the substrate carousel 14. The process chamber 10 is then closed and pumped down to the target vacuum level. As a further arrangement, the flow regulator 34 is manually set to the desired flow rate. (alternatively, consider that the flow regulator is under the automatic control of the sputter controller 40, in which case the regulator is set appropriately according to the values provided in the filter recipe).

Sputter deposition starts as follows: silicon is sputtered from the silicon target 16 by flowing a suitable process gas through the gas inlet manifold 32 and applying a cathode bias voltage, -V, to the target 16 to ionize Ar atoms driven by the electric field. The particular start-up sequence depends on the particular sputter deposition system and other design considerations: for example, in one method, the process gas flow is first initiated, and then a cathode bias-V is applied to initiate sputter deposition; alternatively, the bias may be applied under a flow of inert gas and sputter deposition may be initiated by admitting an appropriate process gas.

During sputtering, the valves VA and VB (and optionally VC) are opened and closed according to the filter recipe 42 and the valve settings of table 50 to deposit SiO₂(and/or optional Si)₃N₄) Layers and a-Si, H, N layers alternate. Based on deposition time and slave calibrationA priori knowledge of the deposition rate obtained by the deposition is used to control the layer thickness. The layer composition is determined based on the process gas mixture controlled by the settings of the flow regulator 34 set based on the calibration deposition (such calibration deposition should also include process parameters such as substrate temperature, target bias (-V), chamber pressure, and total flow rate in the calibration test matrix, as these parameters may also affect the layer composition). After the deposition of the stack of interference filter layers is completed, the process gas flow and bias-V are removed (again, the particular shut-down sequence depends on the particular deposition system, etc.), the process chamber 10 is brought to atmospheric pressure, opened, and the coated substrate 20 is unloaded.

Referring to fig. 4, a diagrammatic view of the interference filter 100 thus manufactured is shown. The filter includes a substrate 102 (e.g., a glass, silicon dioxide, or aluminum oxide substrate initially loaded on the substrate turntable 14) and a-Si: H, N104, and SiO ₂106 and/or Si₃N₄108. In the exemplary interference filter 100, the layer immediately adjacent to the substrate 102 is an a-Si: H, N layer 104, but in other embodiments, the dielectric layer may be immediately adjacent to the substrate. In the exemplary interference filter 100, the topmost layer is the a-Si: H, N layer 104, but in other embodiments the dielectric layer may be the topmost layer. An exemplary stack includes immediately adjacent SiO₂/Si₃N₄Examples of layers, if appropriate to the design, may be included. The exemplary interference filter 100 includes layer stacks 110, 112 on opposite sides of the substrate 102, and in order to fabricate such a device, the sputtering chamber may need to be opened and the substrate "flipped" over the substrate turntable 14. (alternatively, the substrate carousel 14 may be configured such that such manipulation can be performed by a robot without damaging the chambers). Such a filter with two

filter sides

110, 112 may for example be a passband filter, wherein the stack on one side is a high pass filter and the stack on the other side is a low pass filter, the passband then being defined by the wavelength range above the high pass filter cut-off and below the low pass filter cut-off.

A known application of such filters is in applications using silicon detectors. Active devices in which these wavelengths are present in the light source and detectorIs particularly useful. In this spectral region, LEDs and lasers are readily available, inexpensive, large in volume, and efficient. Some major applications include, but are not limited to, infrared gesture control for human-computer (e.g., computer) interaction, infrared night vision for automobiles, LIDAR, infrared night vision for security cameras, and proximity CMOS sensors for mobile phones and elsewhere. In these applications, useful wavelengths are between 700 and 1100 nm. In this range, a-Si: H, N are high index materials suitable for optical applications. Typical refractive index in this range is 3.3 to 3.5, and TiO is used as a comparison₂The refractive index of (A) is only about 2.3 to 2.4. In some suitable embodiments, the a-Si: H, N layer includes between 2% and 8% hydrogen and between 3% and 7% nitrogen, with the balance being Si. Generally, more hydrogen and nitrogen content provides shorter wavelength operation. Typically, nitrogen concentrations as high as 6% to 12% are expected.

In an exemplary embodiment, the a-Si, H, N layer 104 is formed with SiO₂The layers 106 alternate. SiO 2₂Have advantageous properties for this purpose, including good chemical compatibility with a-Si: H, N and a low refractive index (N1.5), which provides a large refractive index step at the interface with a-Si: H, N. However, it is conceivable to replace the SiO by another dielectric layer₂And (3) a layer. For example, the dielectric may not have exact SiO₂Stoichiometries, e.g. SiO₂Can be coated with SiO_xInstead, where x is not exactly two (also referred to herein as "silicon suboxide").

As another example, silicon oxynitride (SiO) may be considered_xN_y) Layer replacing SiO₂As a dielectric layer. In general, when starting from SiO_xAddition of nitrogen to become SiO_xN_yWith nitrogen addition, the refractive index increases with nitrogen content: for example, stoichiometric silicon nitride (Si)₃N₄) Has a refractive index of about 2.0. However, small amounts of nitrogen (i.e., SiO) are contemplated_xN_yWherein x is 2 and x>>y) to improve the interface quality between the a-Si: H, N layer 104 and the adjacent dielectric layer. These compounds provide refractive index tailoring, allowing the construction of new material combinations and continuously varying refractive index configurations.

For arrangingSome suitable design methods to calculate the constituent layer thicknesses and given refractive indices of the constituent layers are based on the following. Typically, the wavelength λ in the layer is defined by λ ═ λ₀N is given, where₀Is the free space wavelength and n is the refractive index. Reflection from a surface with a higher refractive index introduces a phase shift of 180 deg., whereas reflection from a surface with a lower refractive index does not introduce a phase shift. Using these principles and given the refractive indices of the constituent layers, the thicknesses of the constituent layers are chosen such that, for the design-based passband center wavelength, the optical path length through each layer and the optical path length reflected at its interface with the next layer combine constructively, i.e., they are integer multiples of the wavelength. More elaborate interference filter design techniques for selecting the constituent layer thicknesses (and refractive indices if these are also optimization parameters) are given in the following documents: angus Macleod, THIN-FILM OPTICAL FILTERS, fourth edition (Series in Optics and Optoelectronics, CRC Press 2010).

Although the exemplary interference filter includes a repeating unit of two layers, it is contemplated that three or more layers, such as a-Si: H, N layers and two different dielectric layers, may be incorporated into the repeating unit to achieve desired passband properties (e.g., center wavelength of passband, FWHM, "flatness," etc.).

It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. It will be further understood that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.

The following corresponds to the original claims in the parent application, which are now incorporated as part of the specification:

1. an interference filter comprising:

a layer stack comprising a plurality of layers, the plurality of layers having at least:

a nitrogen-added amorphous hydrogenated silicon (a-Si: H, N) layer; and

one or more layers of dielectric material having a refractive index lower than the refractive index of a-Si: H, N.

2. The interference filter of item 1 wherein the one or more dielectric materials comprise SiO₂。

3. The interference filter of item 1, wherein the one or more dielectric materials comprise silicon Suboxide (SiO)_x)。

4. The interference filter of item 1 wherein the one or more dielectric layers comprise silicon oxynitride (SiO)_xN_y)。

5. The interference filter of item 1 wherein the one or more layers of dielectric material comprise a layer of dielectric material having a refractive index in the inclusive range of 1.9 to 2.7.

6. The interference filter of item 5 wherein the layer of dielectric material having an index of refraction in the inclusive range of 1.9 to 2.7 comprises one or more layers comprising Si₃N₄，SiO_xN_y，Ta₂O₅，Nb₂O₅Or TiO₂Wherein y is sufficiently large to provide a refractive index of 1.9 or higher.

7. The interference filter of item 6 wherein the one or more layers of dielectric material further comprise SiO₂And (3) a layer.

8. The interference filter of any of items 1-7, wherein the layer stack is configured to have a passband center wavelength within an endpoint-containing range of 800-.

9. The interference filter of any of items 1-7, wherein the layer stack is configured to have a passband center wavelength within an endpoint-containing range of 750 and 1100 nm.

10. The interference filter of any one of items 1-9, wherein the a-Si: H, N has an atomic concentration of between 1% and 4% hydrogen and between 2% and 6% nitrogen.

11. The interference filter of any one of items 1-10, further comprising:

a transparent substrate supporting the layer stack.

12. The interference filter of item 11 wherein the transparent substrate comprises a glass substrate.

13. The interference filter of any one of items 11-12, wherein the stack of layers comprises a first stack of layers on one side of a transparent substrate and a second stack of layers on an opposite side of the transparent substrate.

14. The interference filter of item 13, wherein the first layer defines a low pass filter having a low pass cutoff wavelength, the second layer stack defines a high pass filter having a high pass cutoff wavelength, and the interference filter has a pass band defined between the high pass cutoff wavelength and the low pass cutoff wavelength.

15. An interference filter comprising:

a layer stack comprising alternating a-Si: H, N and silicon based dielectric layers;

wherein the interference filter has at least one passband centered within an endpoint-containing range of 750-1100 nm.

16. The interference filter of item 15 having at least one passband centered at a wavelength within the range of 800-1100nm inclusive.

17. The interference filter of item 15 wherein the passband center wavelength is 850 nm.

18. The interference filter of any one of claims 15-17 wherein the silicon-based dielectric layer comprises silicon oxide (SiO)_x) And (3) a layer.

19. The interference filter of item 18 wherein the silicon oxide (SiO)_x) The layer containing stoichiometric amounts of SiO₂And (3) a layer.

20. The interference filter of any one of claims 15-17 wherein the silicon-based dielectric layer comprises silicon oxynitride (SiO)_xN_y) And (3) a layer.

21. The interference filter of any one of items 15-20, wherein the a-Si: H, N has an atomic concentration of between 4% and 8% hydrogen and between 2% and 12% nitrogen.

22. The interference filter of any one of claims 15-21 further comprising:

a transparent substrate supporting the layer stack.

23. The interference filter of item 22 wherein the transparent substrate comprises a glass substrate.

24. A method of manufacturing an interference filter comprising alternating a-Si: H, N and SiO_xA layer, the method comprising:

sputtering silicon from a silicon target onto the filter substrate; and

during said sputtering, in (i) the process gas comprises hydrogen and nitrogen to deposit a-Si: H, N and (ii) the process gas comprises oxygen to deposit SiO_xAlternating between them.

25. The method of item 24, wherein the sputtering comprises:

applying a negative bias to the silicon target; and

the inert gas component is included in both (i) the process gas comprising hydrogen and nitrogen and (ii) the process gas comprising oxygen.

26. The method of clause 25, wherein the inert gas is argon.

27. The method of any of items 24-26, wherein the sputtering and the alternating are configured to fabricate an interference filter having a passband center wavelength within the end-inclusive range of 800-1000 nm.

28. The method of any of items 24-26, wherein the sputtering and the alternating are configured to fabricate an interference filter having a passband center wavelength within the endpoint-containing range of 750 and 1000 nm.

29. An interference filter comprising:

an amorphous hydrogenated silicon layer; and

one or more layers of dielectric material having a refractive index lower than that of amorphous hydrogenated silicon, including layers of dielectric material having a refractive index in the inclusive range of 1.9 to 2.7.

30. The interference filter of item 29 wherein the layer of dielectric material having an index of refraction in the inclusive range of 1.9 to 2.7 comprises one or more layers comprising Si₃N₄，SiO_xN_y，Ta₂O₅，Nb₂O₅Or TiO₂Wherein y is sufficiently large to provide 1A refractive index of 9 or higher.

31. The interference filter of any one of claims 29-30 wherein one or more layers of dielectric material further comprises SiO₂And (3) a layer.

32. The interference filter of item 31 wherein the layer stack comprises at least one SiO immediately adjacent to a layer of dielectric material₂A layer having a refractive index within the range of 1.9 to 2.7 inclusive, the dielectric material layer being absent of an intermediate layer of amorphous hydrogenated silicon.

33. The interference filter of any one of items 29-32 wherein the amorphous hydrogenated silicon includes nitrogen.

34. The interference filter of item 33 wherein the amorphous hydrogenated silicon comprising nitrogen has an atomic concentration of between 1% and 4% hydrogen and between 2% and 6% nitrogen.

Claims

1. An interference filter, comprising:

A layer stack comprising a plurality of layers having at least:

a nitrogen-added amorphous hydrogenated silicon (a-Si:H,N) layer; and

one or more layers of dielectric material having a refractive index lower than that of a-Si:H,N; and a transparent substrate supporting the stack of layers;

wherein the layer stack includes a first layer stack on one side of the transparent substrate and a second layer stack on an opposite side of the transparent substrate.

2. The interference filter of claim 1, wherein the one or more dielectric materials comprise _SiO2 .

3. The interference filter of claim 1, wherein the one or more dielectric materials comprise suboxide silicon ( _SiOx ).

4. The interference filter of claim 1, wherein the one or more dielectric layers comprise silicon oxynitride ₍ _SiOxNy ).

5. The interference filter of claim 1, wherein the one or more layers of dielectric material comprise layers of dielectric material having a refractive index in the range of 1.9 to 2.7 inclusive.

6. The interference filter of claim ₅ , wherein the layer of dielectric material having a refractive index in the range of _1.9 to 2.7 inclusive comprises one or more layers including _Si3N4 , _SiOxNy , _Ta2 _O5 , _Nb2O5 or _TiO2 , where _y is large enough to provide a refractive index of 1.9 or higher.

7. The interference filter of claim 6, wherein the one or more layers of dielectric material further comprises a layer of _SiO2 .

8. The interference filter of any of claims 1-7, wherein the layer stack is configured to have a passband center wavelength in the range of 800-1100 nm inclusive.

9. The interference filter of any of claims 1-7, wherein the layer stack is configured to have a passband center wavelength in the range of 750-1100 nm inclusive.

10. The interference filter of any of claims 1-9, wherein the a-Si:H,N has between 1% and 4% hydrogen and between 2% and 6% nitrogen Atomic concentration.

11. The interference filter of any of claims 1-10, wherein the transparent substrate comprises a glass substrate.

12. The interference filter of any of claims 1-11, wherein the first layer defines a low-pass filter having a low-pass cutoff wavelength and the second layer stack defines a high-pass filter having a high-pass cutoff wavelength filter, and the interference filter has a passband defined between the high pass cutoff wavelength and the low pass cutoff wavelength.

13. An interference filter comprising:

Layer stack including alternating a-Si:H,N and silicon-based dielectric layers;

wherein the interference filter has at least one passband having a center wavelength in the range of 750-1100 nm inclusive; and

14. The interference filter of claim 13, having at least one passband having a center wavelength in the range of 800-1100 nm inclusive.

15. The interference filter of claim 13, wherein the passband center wavelength is 850 nm.

16. The interference filter of any of claims 13-15, wherein the silicon-based dielectric layer comprises a silicon oxide ( _SiOx ) layer.

17. The interference filter of claim 16, wherein the silicon oxide ( _SiOx ) layer comprises a stoichiometric _SiO2 layer.

18. The interference filter of any of claims 13-15, wherein the silicon-based dielectric layer comprises a silicon oxynitride ₍ _SiOxNy ) layer.

19. The interference filter of any of claims 13-15, wherein the a-Si:H,N has between 4% and 8% hydrogen and between 2% and 12% nitrogen Atomic concentration.

20. The interference filter of any of claims 13-19, wherein the transparent substrate comprises a glass substrate.

21. A method of manufacturing an interference filter, wherein the method is used to manufacture an interference filter as claimed in any one of claims 1-20.

22. A method of making an interference filter comprising alternating layers of a-Si:H,N and _SiOx , the method comprising:

sputtering silicon from a silicon target onto a filter substrate; and

During the sputtering, alternating between (i) the process gas comprising hydrogen and nitrogen to deposit a-Si:H,N and (ii) the process gas comprising oxygen to deposit _SiOx .

23. The method of claim 22, wherein the sputtering comprises:

applying a negative bias to the silicon target; and

Inert gas components are included in both (i) the process gas comprising hydrogen and nitrogen and (ii) the process gas comprising oxygen.

24. The method of claim 23, wherein the inert gas is argon.

25. The method of any one of claims 22-24, wherein the sputtering and the alternating are configured to produce an interference filter having a passband center wavelength in the range of 800-1000 nm inclusive.

26. The method of any of claims 22-24, wherein the sputtering and the alternating are configured to produce an interference filter having a passband center wavelength in the range of 750-1000 nm inclusive.

27. An interference filter comprising:

A layer stack comprising a plurality of layers having at least:

an amorphous hydrogenated silicon layer; and

one or more layers of dielectric material having an index of refraction lower than that of amorphous hydrogenated silicon, including layers of dielectric material having an index of refraction in the range of 1.9 to 2.7 inclusive;

wherein the layer stack includes at least one _SiO2 layer immediately adjacent to a layer of dielectric material having an index of refraction in the range of 1.9 to 2.7 inclusive, without an intermediate layer of amorphous hydrogenated silicon.

28. The interference filter of claim ₂₇ , wherein the layer of dielectric material having a refractive index in the range inclusive of _1.9 to 2.7 comprises one or more layers including _Si3N4 , _SiOxNy , _Ta2 _O5 , _Nb2O5 or _TiO2 , where _y is large enough to provide a refractive index of 1.9 or higher.

29. The interference filter of claim 27 or 28, wherein the amorphous hydrogenated silicon comprises nitrogen.

30. The interference filter of any of claims 27-29, wherein the amorphous hydrogenated silicon comprising nitrogen has between 1% and 4% hydrogen and between 2% and 6% nitrogen atomic concentration.